This invention relates to a novel fiber, to a nonwoven mat comprising said novel fiber, and to a method of preparing said web. More particularly, this invention relates to a fiber which is prepared from a polymeric blend comprising at least one elastomeric polymer and at least one thermoplastic polymer, to a nonwoven web comprising said fiber and to a method for preparing said melt blown web.
Nonwoven webs containing various polymeric fibers are, of course, well-known in the prior art. Processes for preparing nonwoven mats from thermoplastic fibers have been described in such publications as Naval Research Laboratory Report No. 111437 which was submitted Apr. 15, 1954; NRL Report 5265, which is dated Feb. 11, 1959 and in an article appearing in Industrial and Engineering Chemistry, Vol. 48, No. 8 (1956), pages 1,342-1,346. Such processes are also described in U.S. Pat. Nos. 2,374,540; 2,411,659; 2,411,660; 2,437,363 and 3,532,800. Still other methods for preparing the same or similar nonwoven webs are described in British Patent Nos. 1,055,187 and 1,215,537 and in U.S. Pat. Nos. 3,379,811 and 3,502,763. A method for preparing nonwoven webs from elastomeric fibers by spray spinning a rubber solution is described in U.S. Pat. No. 2,950,752.
As is well known, several of the nonwoven mats heretofore proposed have found utility in a broad range of applications. For example, it is known to use nonwoven mats, particularly those obtained with thermoplastic fibers, in the preparation of battery separators, cable wrap, capacitor paper, as wrapping materials, clothing liners, diaper liners, in the manufacture of bandages and sanitary napkins and the like. Notwithstanding this success, however, the nonwoven mats prepared from thermoplastic fibers do not generally exhibit the delicate balance of properties that would be most desirable in many of these applications. In this regard, it should be noted that the nonwoven mats prepared with thermoplastic fibers are, generally, relatively rigid and firm. These nonwoven mats are, however, generally, non-extensible and do not exhibit any significant softness or hand. Conversely, nonwoven mats prepared with elastomeric fibers are, generally, soft, elastic and resilient. These mats, however, have little if any strength or rigidity. It is, of course, known in the prior art that these deficiencies can, at least, be reduced by laminating the nonwoven mats with other materials, which other materials may be either woven or nonwoven themselves. Even these laminates do not, however, exhibit the delicate balance of extensibility, softness, texture, hand and drape that is desirable for many of the known applications wherein nonwoven mats are used. Moreover, this lack of property balance has limited the areas in which nonwoven mats may be used. The need, then, for an improved nonwoven mat and for a fiber to prepare such a mat is believed readily apparent.